EPICS base-3.15.9 fails to build with GCC-15

["Dmitry Yu. Bolkhovityanov via Tech-talk" <tech-talk at aps.anl.gov>]

Hi!

GCC-14 becomes mainstream (e.g. Debian-13), and familiar base-3.15.6 
fails to build with it.  Fotrunately, 3.15.9 was built successfully, but I 
wanted to check it for "future-proofness" and tried building with GCC-15 
and GCC-16.  It had failed with both.
The test was carried out on Debian-13/x86_64, gcc-15.3.0 and gcc-16.2.0 
built from sources and installed into /opt/.  The commandline is
	make CC=/opt/gcc-15/bin/gcc CCC=/opt/gcc-15/bin/g++

and it results in error compiling src/libCom/flex/ccl.c:


../../../src/libCom/flex/ccl.c: In function 'list_character_set':
../../../src/libCom/flex/ccl.c:155:20: error: too many arguments to function 'readable_form'; expected 0, have 1
  155 |             fputs( readable_form( i ), file );
      |                    ^~~~~~~~~~~~~  ~
../../../src/libCom/flex/ccl.c:143:11: note: declared here
  143 |     char *readable_form();
      |           ^~~~~~~~~~~~~
../../../src/libCom/flex/ccl.c:162:39: error: too many arguments to function 'readable_form'; expected 0, have 1
  162 |                 fprintf( file, "-%s", readable_form( i - 1 ) );
      |                                       ^~~~~~~~~~~~~  ~~~~~
../../../src/libCom/flex/ccl.c:143:11: note: declared here
  143 |     char *readable_form();
      |           ^~~~~~~~~~~~~

(gcc-16 produces the same result).

Old base-7.0.7 had failed in exactly the same way, while the most recent 
base-7.0.10 had built successfully with both GCC-15 and GCC-16.
(A quick inspection shows obvious fixes related to readable_form(), which 
was previously incorrectly declared as "readable_form()" instead of 
"readable_form(int c)".)

The 3.15.9 is currently the latest release of EPICS3, which is still 
widely used.  And there are chances it will become unbuildable on modern 
systems in a year or two.
Maybe the time for base-3.15.10 had come?


With best regards,
Dmitry